SANTIAGO, Chile – After experiencing one of the most powerful earthquakes to strike the earth in more than a century, Chileans accelerated their rescue, aid and security efforts in damaged regions Sunday but also took pride in the comparatively low death toll, a result widely attributed to the country’s meticulous planning and preparation.

The Chilean government dispatched troops to keep order in the hard-hit city of Concepcion, and President Michelle Bachelet opened the door to international aid a day after saying that “we generally do not ask for help.” Her remarks came after a lengthy meeting with advisers convinced her, she said, that the country faces “a catastrophe of such unthinkable magnitude that it will require a giant effort to recover.” Experts said repairs will take years and will probably cost tens of billions of dollars.

While the death toll rose steadily to more than 700, according to a midday estimate, it remained a small fraction of the tally from a far less powerful earthquake last month in Haiti that claimed at least 220,000 lives. That temblor was more shallow and much closer to a large population center, the Haitian capital, Port-au-Prince. But the deaths there were mostly because of widespread building collapses, which Chilean cities did not experience.

Earthquake scientists, building engineers and political scientists in Chile and the United States agreed that even though half a million homes were heavily damaged during more than 120 seconds of shaking, the fact that so many Chileans survived was a testament to the nation’s enactment and enforcement of stringent building codes.

“We would have expected that an 8.8 earthquake would have done a lot more damage,” said Paul Caruso, a geophysicist with the National Earthquake Information Center in Golden, Colo. “The people in Chile have experience with earthquakes that saved hundreds if not thousands of lives.”

The earthquake, centered 200 miles southwest of the capital, was one of at least a dozen in Chile since 1973 that were larger than magnitude 7. The quakes release stresses between two tectonic plates that are moving past each other at a rate roughly one-third faster than the plates that define the San Andreas fault in California, according to Jonathan Bray, a professor of geotechnical engineering at the University of California at Berkeley.

“Unlike in Haiti, people think about earthquakes all the time in Chile. It’s in their mind,” said Michael Shifter, vice president for policy at the Inter-American Dialogue think tank in Washington. “This is a country that can mobilize resources and meet these national challenges.”

Chile has relatively low levels of corruption, making enforcement of building codes more credible than in other Latin American countries; its rank on Transparency International’s Corruption Perceptions Index is 25, just six spots below the United States, while Haiti’s is 168.

Several U.S. disaster relief experts cautioned, however, that the Chilean government should be careful not to become overconfident. While Bachelet said at her news conference Sunday that the country needed field hospitals, water-purification plants, temporary bridges and experts in damage assessment, her plea was not immediately conveyed through official channels to Washington or the International Red Cross.

“We have resources that are positioned to deploy, should the Chilean government ask for our help,” President Obama said after speaking with Bachelet on Saturday. But Virginia Staab, the State Department’s spokeswoman for Western Hemisphere affairs, said late Sunday that while the United States has placed some search-and-rescue teams, field hospitals and medics on alert, “there have been no official requests right now.” The only U.S. aid provided so far, she said, was small amounts of water and food, as well as satellite communications and imagery of areas that have not yet been reached by rescue personnel.

Speaking of Bachelet’s statement, Staab said, “If she is looking for all of those [items] from us, we will likely provide them.” She added that Washington was hoping for some “clarity” by Monday morning on Chile’s request.

Secretary of State Hillary Rodham Clinton, who has long planned to spend this week in Latin America, will arrive in Santiago on Tuesday morning, officials said. Once there, she intends to reiterate the administration’s willingness to assist.

The Red Cross released a statement Sunday calling the earthquake the worst disaster to hit Chile in 50 years — another major temblor occurred in 1960 — and said that six of Chile’s 15 geographic zones received catastrophic damage. So far, the American and international chapters of the Red Cross have released several hundred thousand dollars to their Chilean affiliate to fund search-and-rescue and first-aid efforts.

But Tracy Reines, director of the American Red Cross’s international response center, said that “we’re standing by, waiting” for a government request for more substantial aid. She noted that “you certainly want to get assistance quickly, but it does not have to be international assistance. . . . It can come from within Chile.”

Julia E. Sweig, director for Latin America studies at the Council on Foreign Relations, said Chile will probably accomplish a lot on its own. “The Haiti and Chilean experiences dramatize the enormous differences between what we sloppily think of as one region. In Chile, you have an investment over decades in creating functioning institutions with a reliable tax base that produces a revenue stream with accountability of elected leaders. You have a functioning state and solid governance” that will make its response significantly better, Sweig said.

Police said more than 100 people died in Concepcion, one of the country’s largest cities, about 70 miles from the epicenter. Dozens of people were trapped inside a 14-story building that toppled, and at least 20 bodies were removed as teams of firefighters crawled through the wreckage, searching for signs of life. The Associated Press reported that 16 people had been pulled out alive. The city’s university caught fire as gas and power lines snapped. Many streets were littered with rubble.

As food, water and gasoline become scarce in Concepcion, looting erupted. Police using tear gas initially attempted to stop the looters. A battle developed inside a supermarket and ended only when police allowed local residents to form long lines and remove essential items for free. Jacqueline van Rysselberghe, the mayor of Concepcion, said, “We are going to have social explosion if aid is not received today.”

The Chilean air force sent a 747 filled with police officers to the region in an attempt to regain control. Military roadblocks were set up outside some cities to keep outsiders from joining the looting. Francisco Vidal, the Chilean minister of defense, announced a curfew and said 10,000 troops will be sent to the areas most affected by the earthquake.

At sunrise on Sunday, those who attempted to reenter their damaged homes to retrieve goods and food were forced to evacuate again when a powerful 6.3-magnitude aftershock hit, further complicating rescue efforts. But by midday, emergency workers from the capital had fanned out to a 375-mile stretch of coastline where the majority of the residents have no access to food, water or electricity. Communication with even larger cities was sporadic, while many minor outlying villages and smaller cities had not been reached by day’s end.

“Our biggest problem is in the Juan Fernandez region [the Robinson Crusoe Islands],” said Ivan de la Maza, regional governor of the hard-hit Valparaiso region. Multiple ocean swells estimated at 30 feet — 10 times as high as the relatively mild tsunami waves that reached Hawaii — demolished the islands’ coastal villages, 415 miles west of the mainland.

Residents there did not feel the earthquake, and most of them were asleep when huge ocean swells flooded the town at 6 a.m. Saturday. When rescue crews arrived Sunday, they found that the tsunami had churned houses and boats into mountains of debris before pulling them back into the Pacific. Aerial photos reveal streets that have been wiped off the map. The islands are home to an estimated 600 permanent residents, with 200 tourists believed to be visiting, many at waterside bed-and-breakfasts.

With most homes built of wood and lightly balanced on foundations, the structures first floated inland, then were smashed by subsequent swells described by the local mayor as “a train” of 10-foot-high waves.

In Santiago, thousands of families dragged their mattresses outside to sleep on the streets, fearing aftershocks.

“No one brings us anything. We are stuck here,” said Daniel Garcia, 28, a Peruvian immigrant who spent the night in the Barrio Brazil neighborhood, sleeping on the street with his family. The family dragged mattresses down two flights of stairs, piled a television atop a stack of rubble and used wreckage to build a makeshift shelter.